Radio receiving circuit



Oct. 9, 1928. 1,686,621

s. LOEWE RADIO RECEIVING CIRCUIT Filed Nov. 12, 1926 iur iumnmt IIIIIIIIIIP v INVENTG'R SlEGMUND LOEWE mam N "w TORNEY resistance coupledamplifiers fundamentally Patented 0a. 9, 1928.

UNITEDSTATES SIEGMUND I name RECEIVING CIRCUIT] Application filedNovember 12, 1926,'Seria1 no. 147,971, a1it1 in Germanybctober 21, 1925.

- This invention relate's'to a receiver arrangement and moreparticularly to a receiving cir-b cuit using an intermediate-frequencyamplifier. 1 A number of recelvlng'arrangements work with anintermediate or beat frequency which is produced by a localoscillatorwhose fre:

quency differs from the incoming 'wave by the intermediate or beatfrequency. In receiver apparatus of the said sort, it iscustomaryaccording to former practice, 'touse interme diate-frequencyamplifiers comprisingth'ree or four amplifier stages which areinter-wcoupled by tuned systems. For example, for. superheterodyne andultradyne circuitar-. rangements, it is customary to use intermedt'ate-fr'equencyamplifiers coupled by tuned transformers,- or inductioncoils. Tuning when such intermediate-frequency amplifiers were used wasan absolute necessity for two reasonstl) because sensitive famplifiersfor. higher frequencies could be built with only 'tunedcouplingmeans,and (2) because sharp selection of the intermediate-frequency" amplifierhas been the most decisive'point indeterminingthe selectivityoftheentirefreceive -1ng apparatus. Hence, it seems ob'mou'sthat appearedunsuitedfor this purpose. I

An object of this-inventlon conslsts in the creation of 'a highlyselective; intermediate amplifier comprising-the use'of aperiodicallyinter-coupled amplifierstages'. 5

Another object of this inve tion of any chosen intermediate frequencymay be easily and efficiently accomplished.

A'further object of-this invention is to pro- It will be understood thatevery aperiodicradio frequency amplifier can be changedin'to a selectiveamplifier by tuning the input circuit of the aperiodic amplifier to thewave to tuned to half the frequency of'the incoming be amplified. By thecombination of an aperiodic amplifier witha tuned: circuit, there ceedsthese demands on "two counts. The comblnation as before suggested,renders it possible to readily alter'the frequency to V which theintermediate-frequency amplifier low frequency amplification in one andthe is used to produce amplification of bothinter} ntion i's toprovideanarrangement whereinjthe amphfica-.

coupledby tuned inductance coils, or "oscillafrequency, as many.resettings in tuning are LoEwE, F 'BERL IN, nnrnnnnau, amaneissmma T0RApIo con ronarron on. amnnrcm a oonronA'rIon orpnnewann.

has been tuned. In the'case of amplifiers tion circuits, upon alteringthe intermediate the tuning of The operation and constructionofsuch an Iamplifier is simpler, and its utility issubstantially greater than thatof amplifiers hereto- I fore .used. pp

' But a further advantage and merit, is that oneandthe same amplifiercan without any" trouble be employed .as an intermediate-frequencyamphner and asa low frequency amplifie'r. Itiseven' feasibleto usethesame amplifier for radio frequency, intermediate, and

SELIDQI-QCGlVQI circuit arrangement.

In the accompanying drawings Figure 1 is.

a. wiring "diagram showing an arrangement wherem. a single. reslstancecoupled amplifier mediate and audio frequency currents and Figure 2shows "the 'connect ons whereby'a the use of intermediate frequency. 1is the aerial, 2 algrid circuit tuned to the incoming,

. wave, 3, 4,5, 6,7,8 are amplifier tubes. I The plate circuit of thetube3, byway of then'eu tralized coil 9,?i's1brought to the-positiveterminallO of the'joint plate battery, All of'the f filaments of thetubesfare l connected- 11 p allel between thefjoint negative pole: 11and Jthe positive' pole 12. The grid circuit 2 isbranched off from apotentiometer 30. ,v The radio-frequency current amplified-by thefirst-stagetube 3. is fed to the grid circuit 13 of tube 4 .which actsas a combining tube and I which is supplied with potential from the re-vgeneratively coupled, tube 5 which is usually loowave,being'slightly'detuned with reference cuit 16 is given a very sharpselectivity. In

case it is intended to alter the intermediate frequency, all that isnecessary is to change the tuning of circuit 16 to the desiredintermediate frequency in order to thereby readjust the entireintermediatefrequency amplifier to the modified intermediate frequency.

grids having also leaks consisting of high- Ol1II11C reTaistancesZ'l,22. In the output circuit is'connected a "telephone receiver, 23

' shunted by a bypass condenser 23 and also frequency componentresultingfrom the rec;

tification efiect of the radio frequency tube. 3 The resistance-coupledamplifier is in 'aposi '20 inction as intermediate-frea condensershunted transformer 24: which feeds the grid of tube 6 again with thelow tion, Without its quency amplifier ibeing thereby impaired, toproduce an efiicient low frequency amplification; Now, if the amplifier6, '4, 8-is to be 7 used at the same time for radio frequencyamplification, first-stage tube 3 together with its circuitappurtenances is omitted. This is shown in Fig. 2. The grid circuit 2(Fig. 2). is then inserted at the point of the grid lead 1 of tube 6markedby a cross (see Fig. 1) and so causes the antenna to transferenergy to this circuit. In the plate circuit of tube 8 is. I furtherconnected, at tlie placc marked by a cross (see Fig. 1 a coil 22 whichis caused to act inductively upon thecoil of the grid circuit13 (seeFig.2). Nhatre'mains of-the circuit arrangement'are five tubes only,i."e., the modulator tube 4,the generator tube5and the threeresistance-coupled amplifiertubes 6, 7 8, which act at the same time aslow frequency intermediate-frequency, and radio frequency amplifiers.-

Figure 2 shows completely this modification where the sensitivityattained by virtue of this arrangement is extremely high. The. 7operation of the system, shown in Fig'. 2 is, brieflv, as follows.Circuit 2 is tuned to the desired incoming signal and the resultingvariations in potential across it are applied Circuit 15 feeds into 16the resulting interme- 'diate frequency energy Whichin'turn is fed tothe input side of tube 6. This intermediate frequency energy is thenamplified and detected by tubes 6,? and 8. The 'audio frequencycomponent of the energy appearing in the plate circuit of tube 8 willthen be're-' fiexed into tube 6 by means of transformer 24;, an'iplifiedby tubes 6, 7 and S and then be of a sufficient amplitude to actuatereceivers 23.v

In this manner the resistance"coupled ainpli-fier system 6, 7 and 8isutilized to effect rad-i0, intermediate and audio frequency amplificationsw y i c Having thus described my invention, What I claim is:c' r 1 ln adio receiving apparatus, a tunable input circuit; a radiofrequency amplifier comprisinga vacuum tube having a control elec trode,a cathode-and an-anode; a source of potential for energizing the cathodeof Said tube; a resistance across said source of potential connectionsfrom said tunable input circuit to said control electrodeand'resistance;

means for heterodyni-ng the output of" said amplifier means foramplifying the interme- V diate frequency caused by said heterodyning,

said last mentioned means comprising plurality of resistancecoupled-amplifier tubes, a plurality of which have grid leak resistancess5 connected across-their control electrodesand filaments; and means;for refiexing the output ing the resulting audio frequency oscillations.

' sineMuun Loe s.

CERTIFICATE OE CORRECTION. Patent No. 1,686,621. Granted October 9,1928, to

SIEGMUND LOEWE.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1,line 25, after the word "coil" for the numeral "22" read "32"; and thatthe said Letters Patent should be read with this correction therein thatthe same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of January, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents.

